Rollcage 2 IMG

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IMG + IDX

• Format type: Archive
• Endianness: Little-endian

Format Specifications

// IDX FILE

// for each file

uint32 {4}   - File Offset

uint32 {4}   - Compressed File Length

uint32 {4}   - Decompressed File Length

uint32 {4}   - Unused

// IMG FILE

// for each file

char {4}     - File Header (GT20)

uint32 {4}   - Decompressed File Length

uint32 {4}   - Unused (Same as the Unused field in the IDX File)

uint32 {4}   - Length of additional Information

char {X}     - Additional Information

byte {X}     - Compressed Data

Compressed Data:

uint32 {4}   - 'ControlBits'

char {X}     - Compressed Data

uint32 {4}   - 'ControlBits'

char {X}     - Compressed Data

..

The ControlBits say how to decompress the data.

If the Bit is 0 then the next Byte is not compressed, and copied directly from the Input buffer

If the Bit is 1 then the next Bytes are compressed. The next ControlBit shows how it is compressed.

The Next Bit is 0:

The decompressor reads the next Byte from the Input buffer.

This Byte-256 tells the decompressor how many bytes to go back in the Output buffer.

From that position the decompressor copies 2 bytes to the end of the already decompressed Data.

If the next ControlBit is 1 the decompressor copies 2 additional Bytes.

If the next ControlBit is 1 the decompressor copies 1 additional Byte.

The Next Bit is 1:

The decompressor reads the two next Bytes from the Input buffer.

The first three bits of theese is the number of bytes to copy-2.

The remaining 13 bits-8192 tells the decompressor how many bytes to go back in the Output buffer.

If the number of bytes to copy is 0, the decompressor reads also the next byte from the Input buffer.

The first bit of this byte indicates that another 8192 should be deducated from the position from where the bytes have to be copied.

The rest is the number of bytes to copy-2. If this is again 0, the decompressor have to read the next 2 bytes, which is the exact number of bytes to copy.

Example:

MultiEx BMS

Not written yet

Notes and Comments

• The *.IDX file contains the directory, the *.IMG file contains the data

Supported Programs

• Game Extractor